[Campbell Biology P.1029] According to the 'Energetics of Osmoregulation' section, which of t... | Practice Question

According to the 'Energetics of Osmoregulation' section, which of the following statements regarding the energy cost of osmoregulation is correct?

  • A: Maintaining a large osmotic difference between body fluids and the environment always leads to a lower energy cost.
  • B: Freshwater molluscs typically maintain body fluid osmolarity significantly higher than marine molluscs to minimize energy cost.
  • C: For brine shrimp, osmoregulation can account for as much as 30% of their resting metabolic rate due to the large osmotic gradient.
  • D: Osmoregulators primarily use passive diffusion to manipulate solute concentrations in their body fluids, thereby saving energy.

Explanation

The text states: 'For brine shrimp, small crustaceans that live in extremely salty lakes, the gradient between internal and external osmolarity is very large, and the cost of osmoregulation is correspondingly high—as much as 30% of the resting metabolic rate.' This directly supports option C. Options A and D contradict the text regarding energy cost and active transport, respectively. Option B is incorrect as freshwater molluscs have much lower osmolarity than marine ones, minimizing osmotic difference.